This invention relates to method and apparatus for the transfer of heat from gases containing entrained solids. In accordance with another aspect, this invention relates to carbon black production and to an improved method and apparatus for perheating an oxygen-containing gas, such as air being passed to a carbon black production furnace. In accordance with a further aspect, this invention relates to a control system for controlling the flow of an oxygen-containing gas, such as air used for supporting combustion in a carbon black furnace passed in indirect heat exchange with carbon black effluent reaction smoke. In accordance with a further aspect, this invention relates to a control system which manipulates the flow of oxygen-containing gas around a preheater responsive to temperatures falling below a predetermined minimum for the carbon black smoke exiting from the preheater.
Various procedures are known for preparing carbon black by the breakdown of gaseous or vaporized hydrocarbons through incomplete combustion. In the production of carbon black by incomplete combustion of an oil feed stock in a carbon black furnace or reactor, it has been found that the effluent from the carbon black reaction provides an economical source of heat to preheat combustion air or oil feed, produce steam, and the like. The carbon black furnace or reactor effluent has ample temperature for preheating various streams passed to the individual furnaces but the reactor effluent temperature is not constant. Variation in the rate of introduction of quench water at the outlet end of the carbon black reactor obviously causes variation in effluent temperature. Also, variations in quench water rate of flow alters the temperature of the furnace effluent. The rate of flow of reactor effluent varies also for other reasons, as from irregularity in gas and air flow tangentially into the furnace as well as variations in flow of charge stock to the furnace. All of these variations and irregularities in flow directly cause variations of reactor effluent temperatures. Furthermore, streams to be heated entering the indirect heat exchange units can vary somewhat in temperature as from day to night and night to day.
In some instances the carbon black reactor effluent stream temperature drops too low, which causes low velocities and in turn brings about fouling of the indirect heat exchange surfaces used to preheat air or other materials. The present control system maintains the temperature of the carbon black reactor effluent exiting the preheater above a minimum level, thereby minimizing deposition of carbon on the heat exchange surfaces.
Accordingly, an object of this invention is to provide an improved waste heat recovery system.
Another object of the invention is to provide a method and apparatus for utilizing available heat from a carbon black furnace effluent.
Still another object of the invention is to provide a method and apparatus for preheating air to a carbon black furnace.
Another object of this invention is to provide a control system for regulating the flow of heat exchange fluids so as to minimize fouling of heat exchange surfaces.
Other objects, aspects, as well as the several advantages of the invention will be apparent to those skilled in the art upon reading the specificiation, drawing, and appended claims.
The drawing illustrates, in diagrammatic form, one arrangement of apparatus parts for carrying out the objects and realizing the advantages of this invention.